Add isBeforeDate, isAfterDate, isSameDate

snippets/lcm.md

@@ -8,7 +8,7 @@ The GCD formula uses recursion.
 ```js
 const lcm = (...arr) => {
   const gcd = (x, y) => (!y ? x : gcd(y, x % y));
-  const _lcm = (x, y) => (x * y) / gcd(x, y);
+  const _lcm = (x, y) => x * y / gcd(x, y);
   return [...arr].reduce((a, b) => _lcm(a, b));
 };
 ```